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Peroral CT Enterography with Lactulose Solution: Preliminary Observations

Halil Arslan¹, Ömer Etlik¹, Mustafa Kayan¹, Mustafa Harman¹, lyas Tuncer² and Osman Temizöz¹

¹ Department of Radiology, Yuzuncu Yil University Faculty of Medicine, Arastirma Hastanesi Radyoloji, Maras Cad. 65200, Van, Turkey.
² Department of Gastroenterology, Yuzuncu Yil University Faculty of Medicine, Maras Cad. 65200, Van, Turkey.

Received March 22, 2004; revised September 22, 2004;

 
Address correspondence to H. Arslan (drhalilarslan{at}hotmail.com).

Abstract

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OBJECTIVE. The objective of our study was to evaluate lactulose solution as a new oral contrast agent with the use of peroral CT enterography to determine the adequacy of luminal distention and conspicuity of the bowel wall.

CONCLUSION. Peroral CT enterography performed with lactulose solution is a simple and noninvasive method of evaluating the small bowel by obtaining good distention. It can also be used at routine abdominal examinations as a negative contrast agent instead of iodinated oral contrast medium, especially for CT angiography.

Introduction

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The techniques for diagnostic imaging in patients with smallbowel disease have changed dramatically in the past decade. Several years ago, the only methods to assess the small bowel were conventional enteroclysis or a small-bowel follow-through. In recent years, with the introduction of helical scanning and then MDCT technologies, the accuracy for diagnosing digestive tract diseases with CT has been highly improved, and CT is used more and more in the evaluation of patients with suspected gastrointestinal disorders. Within this context, CT enterography, which is also referred to as "CT enteroclysis," was developed to enable the evaluation of luminal, extraluminal, and mural alterations of the small bowel [1–4].

Just as the success of all other imaging strategies targeting the small bowel is predicated on adequate intestinal distention, so too is the success of CT of the small bowel predicated on adequate intestinal distention with a luminal contrast agent. Numerous enterography techniques have been designed to optimize visualization of the small bowel. Most of these studies have used fluoroscopic placement of a nasojejunal feeding tube to infuse oral contrast agent. Although this technique provides excellent image quality, most patients find placement of this nasojejunal feeding tube onerous and many patients perceive duodenal intubation as traumatizing. Clinical implementation of enterography techniques has been slow, which thereby taints the noninvasive character inherent to most other forms of imaging [4, 5].

For small-bowel imaging to gain wider clinical acceptance, the features of noninvasiveness need to be retained. Thus, contrast agents that provide distention need to be administered orally without duodenal intubation. Unfortunately, after oral administration, water is rapidly resorbed in the small bowel, and bowel distention is diminished. Resorption of water can, however, be inhibited with certain additives [5–7].

Imaging of the small bowel without intubation has also been proposed. Numerous CT enterography techniques have been designed to optimize visualization of the small bowel, and various contrast agents were used for luminal opacification. A major limitation of all these protocols for small-bowel imaging without intubation is the lack of adequate distention of the intestinal lumen, which is considered a prerequisite for a detailed and accurate evaluation for small-bowel abnormalities and disease. Subtle mucosal abnormalities may be missed in a collapsed loop, and inadequate distention may simulate wall thickening or abnormal enhancement [8–10].

The purpose of our report is to describe and evaluate lactulose solution as a new oral contrast agent with the use of noninvasive peroral CT enterography to determine the adequacy of luminal distention and conspicuity of the bowel wall.

Materials and Methods

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Subjects
Fifty patients who had been referred for abdominal CT examination because of symptoms suggestive of different abdominal diseases were included in this study (23 females and 27 males; age range, 8–82 years; mean age, 47.2 ± 13 [SD] years). Peroral CT enterography was performed after explanation of the goal and procedure of this study to each patient. The use of an oral contrast agent was necessary in all patients; instead of using an oral iodinated contrast agent, we used diluted lactulose solution for examination of the small bowel. Exclusion criteria were history of abdominal surgery or radiation treatment, possibility of bowel obstruction, galactose intolerance, and inability to tolerate a 20-sec breath-hold during abdominal examination.

View larger version (112K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A —Examples of poor, good, and optimal small-bowel distention on CT. CT image of 39-year-old man shows less than 40% of small-bowel distention (poor distention).

View larger version (110K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B —Examples of poor, good, and optimal small-bowel distention on CT. CT image of 44-year-old woman shows 40–70% of small-bowel distention (good distention).

View larger version (110K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C —Examples of poor, good, and optimal small-bowel distention on CT. CT image of 42-year-old woman shows more than 70% of small-bowel distention (optimal distention).

Lactulose is a synthetic disaccharidase that results from combining galactose and lactose. Its underlying chemical structure prevents intestinal absorption, and its inherent osmotic property leads to increased bowel distention. To our knowledge, solutions of lactulose have not been used for smallbowel imaging to date. Twenty milligrams of hyoscine-N-butyl bromide (Buscopan, Boehringer Ingelheim) was IV administered to patients just before scanning to achieve intestinal hypomotility.

CT Enterography
The patients fasted for at least 5 hr before the examination without any other digestive preparation. CT was performed after 1,250 mL of the diluted lactulose solution had been ingested. The CT images were acquired from the diaphragm to the symphysis pubis. After IV administration of 100 mL of nonionic contrast medium at a flow rate of 2.5 mL/sec, MDCT acquisition (Somatom Sensation 4, Siemens Medical Solutions) was performed at 70 sec using 3-mm slice thickness and 3-mm collimation with 367 mA and 120 kVp. The mean radiation exposure dose was 9.5 mGy. Images were reconstructed every 3 mm. The breath-hold period was 20–25 sec.

Image Evaluation
The technical quality of distention was determined in consensus interpretations by three investigators. All images were evaluated at a postprocessing workstation (Leonardo, Siemens Medical Solutions). Observers assessed images of the jejunum, ileum, and ileocecal regions. They discussed their interpretations on a segment-by-segment basis, and the final decision was determined by consensus. If their interpretations differed, they were made aware of all the data for the case in question. Small-bowel distention, wall conspicuity, homogeneity of opacification, and the presence of artifacts were subjectively evaluated.

View larger version (112K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A —Normal appearance of small bowel on transverse CT enterography images. Image shows optimal distention of jejunal loops in healthy 28-year-old man. Note valvulae conniventes.

View larger version (89K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B —Normal appearance of small bowel on transverse CT enterography images. Image of same patient shows good distended normal ileal loops.

View larger version (101K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A —Optimal appearance of small bowel on CT enterography. Constant homogeneity, wall conspicuity, and demarcation of bowel content from surrounding tissues were optimal in image of distal ileal segment in 39-year-old man with abdominal pain (A) and good in image of jejunum (B) in 44-year-old woman with right lower-quadrant pain.

View larger version (98K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B —Optimal appearance of small bowel on CT enterography. Constant homogeneity, wall conspicuity, and demarcation of bowel content from surrounding tissues were optimal in image of distal ileal segment in 39-year-old man with abdominal pain (A) and good in image of jejunum (B) in 44-year-old woman with right lower-quadrant pain.

Adverse Effects
All the patients were interviewed about their tolerance of the procedure 1 and 24 hr after each examination. Patients were asked about the taste of the solution and whether they experienced nausea, vomiting, abdominal discomfort, or diarrhea in association with ingestion of the contrast agent. All these parameters were classified on a standardized questionnaire with a 3-point scale (i.e., score of 0, no side effects; 1, mild side effects; 2, severe side effects) for this purpose.

Results

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The large dose of oral contrast medium was well tolerated and provided adequate luminal distention in most patients. There was no artifact in all patients. The jejunum showed optimal distention in 16 patients, good distention in 21, and poor distention in 13, whereas the ileum showed optimal distention in 25 patients, good distention in 21, and poor distention in four. Good to optimal evaluation of the ileocecal region was obtained in all patients (Fig. 2A, 2B). Constant homogeneity of opacification was optimal in the jejunum and good to optimal in the ileum and ileocecal regions. Wall conspicuity and optimum demarcation of bowel content from the surrounding tissues were good in the jejunum and optimal in the ileum and ileocecal areas (Fig. 3A, 3B). Bowel caliber evaluated at the levels of the jejunum and the ileum measured an average of 22.5 mm (range, 16–25.4 mm) and 17.8 mm (range, 15.1–23 mm), respectively; wall thickness measured an average of 2.6 mm (range, 2–2.9 mm) at the level of the jejunum and 2.4 mm (range, 1.7–2.9 mm) at the level of the distal ileum (Table 1).

On CT evaluation, the addition of multiplanar reformations to conventional axial images did not reveal additional abnormalities; however, multiplane imaging significantly improved the observers' confidence in their interpretations of the images. Especially cystic lesions such as pancreatic pseudocyst, ovarian cyst, or focal ascites around the small bowel could be misdiagnosed (Fig. 4), but they were identified easily using dynamic evaluation and multiplanar reconstruction images in our study. In addition, coronal multiplanar reconstructions were also useful in the interpretation of the ileocecal region (Fig. 5A, 5B). On the other hand, coronal reformations were similar to conventional abdominal radiography, and clinicians are more familiar with these images than with the axial images.

View larger version (71K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4 —CT enterography image of 57-year-old woman with ovarian cyst shows that left ovarian cyst could not be definitely differentiated from surrounding intestinal segment because cyst is same density as intestine.

View larger version (100K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A —Coronal multiplanar reconstructions from CT enterography. Images show that ileal segments in 42-year-old woman with occult intestinal bleeding (A) and terminal ileum-ileocecal region in 39-year-old man with abdominal pain (B) were clearly differentiated.

View larger version (125K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5B —Coronal multiplanar reconstructions from CT enterography. Images show that ileal segments in 42-year-old woman with occult intestinal bleeding (A) and terminal ileum-ileocecal region in 39-year-old man with abdominal pain (B) were clearly differentiated.

View larger version (5K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6 —Bar graph shows rates of intestinal distention achieved. In each group, from left to right, bars show percentage of poor, good, and optimal distention.

Discussion

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Enteroclysis is the primary examination method of the small bowel, and it is superior to CT in the evaluation of mucosal detail and valvulae conniventes. Enteroclysis is also superior at showing the location of an abnormality along the length of the intestine. However, conventional enteroclysis has several major disadvantages: the limited information regarding extramural extension of the disease, limited capability for assessing overlapping bowel loops, complications associated with the examination, and the radiation dose to patients, most of whom are young.

CT enterography provides adequate image quality. The inherent advantages of CT enterography over conventional enteroclysis are the potential to detect extraluminal abnormal conditions and the ability to provide detailed information about the wall of the small bowel and the entire abdomen. It is also superior for the direct visualization of the submucosa and muscularis propria. Unlike conventional enteroclysis, CT enterography does not have problems showing overlapping bowel loops. Recent reports suggest that this method can be used successfully for the evaluation of small-bowel diseases.

MR enterography can also be used in the same way as CT enterography. In addition, MR enterography does not expose the patient to radiation, provides functional information, yields images with superior soft-tissue contrast, and has multiplanar imaging capabilities. However, CT enterography is used in the abdomen, especially for the evaluation of gastrointestinal system disease, more than MR enterography because CT enterography has some advantages over MR enterography for the evaluation of the abdomen, such as quick examination and capabilities of revealing abnormalities of the abdomen without any artifact [8, 11–13]. For these reasons, we prefer CT enterography using peroral lactulose solution over MR enterography.

In CT enterography, luminal distention is required for small-bowel imaging because collapsed bowel loops can hide even large lesions and may falsely mimic wall thickening. Even in patients with small-bowel disease, bowel loops are often collapsed and imaging can be difficult [14]. Small-bowel distention can be achieved with intubation with a catheter through a nasojejunal or peroral route or together with endoscopy, and luminal opacification is based on the administration of an appropriate contrast medium [8, 15–17].

A duodenal tube can be placed using fluoroscopic guidance. The mean fluoroscopy time was 11.2 min (range, 5.7–32.8 min). The mean radiation exposure during fluoroscopy for the placement of the enteroclysis catheter is 6.4 mGy (range, 3.3–14.6 mGy) and 9.5 mGy in MDCT in abdominal examinations. However, in addition to exposing patients to considerable radiation, which is particularly undesirable for many patients, the technique requires the use of two diagnostic rooms and movement of the patient between examinations. Furthermore, placement of the tube is considered traumatizing by many patients and, thereby, limits patient acceptance [5].

Imaging of the small bowel with noninvasive adequate distention of bowel loops is possible without fluoroscopically guided duodenal intubation. The use of various oral contrast agents, both positive and negative, has been proposed. Most investigators use water because of its favorable signal properties. Water is relatively safe, although water overload, vomiting, and related aspiration remain potential risks. The major limitation of this method concerns early water reabsorption, which prevents visualization of the ileocecal region in more than 30% of patients. Adequate luminal distention can be achieved by the administration of a different negative or positive contrast agent. Oral contrast agents, including water and water in combination with mannitol, a bulk fiber laxative, locust bean gum, and a combination of mannitol and locust bean gum, have been reported [5, 7, 18–21]. However, none of these has proved sufficiently successful to be widely used clinically, and research on this subject is ongoing.

We propose a noninvasive method that allows adequate distention: We used a solution composed of water and lactulose for small-bowel distention. Our method permitted noninvasive high-quality imaging of the small bowel. The lactulose solution was easily ingested by each patient and did not cause substantial serious clinical side effects. Good luminal distention, optimum constant homogeneity, and optimum demarcation of the bowel content from the surrounding tissues were obtained in most cases.

With the addition of lactulose, the resorption of water can be sufficiently slowed to ensure homogeneous small-bowel distention after oral administration of water. Once in the small bowel, the unabsorbable and unfermentable lactulose remains unmodified and linked with water molecules, fills the lumen, and distends the intestinal loops [22]. The effect of lactulose was seen mostly in the distal ileum in our study. The terminal ileum and cecum also were clearly shown.

Most small-bowel diseases affect the terminal ileum, and this area should be visible for diagnosis. In this study, we found that the terminal ileum could be seen very clearly in most patients; we believe that we can better see terminal ileum, which is the area that is most affected in inflammatory disease of the small bowel, with lactulose solution as the contrast agent. If the delay time chosen was longer than 50 min, the other parts of the colon could also be evaluated optimally without the need to administer any contrast agent via the rectal route.

Negative oral contrast agents are becoming more important than previously in MDCT because clinical use of CT for imaging the abdominal vasculature and urinary tract has increased. Optimal evaluation of the vascularity on maximum-intensity-projection and multiplanar reconstruction images could not be achieved with the administration of a positive oral contrast agent. This is important for the diagnosis of vascular diseases such as mesenteric thrombosis, small-bowel infarct, atherosclerotic process, or gastrointestinal bleeding [20, 23, 24]. For these reasons, diluted lactulose solution instead of oral iodinated contrast medium can be used not only in the diagnosis of small-bowel disease, but also in the diagnosis of the other abdominal diseases for small-bowel opacification in routine abdominal examination.

We have seen some limitations in the use of lactulose solution. First, slightly more side effects were associated with the lactulose solution than with other contrast agents. Slight nausea and abdominal discomfort that subsided without treatment were the most frequent side effects. The symptoms were not serious, and treatment can be available in this context even if it is necessary. On the other hand, water digestion can also cause nausea and vomiting from overloading a large volume of liquid. In addition, some of the patients in our study were old and had abdominal malignancies or serious health problems. These other conditions can also cause nausea and abdominal discomfort. In our study, most of the patients who suffered slight nausea and abdominal discomfort were old and had malignancy. Few problems were seen in our young patients.

The second disadvantage associated with the use of lactulose solution was in the differential diagnosis of intra- and extraluminal fluid collections such as local ascites, cystic lesions, or abscesses. However, we used a workstation for the report and to differentiate the bowel wall from the lesion. Because of the 3D applications available on the workstation and its capability for quick dynamic evaluation of consecutive cross-sectional images and multiplanar reformations, we found that differentiation of the bowel wall from the lesion was not difficult. In our study, cystic intraperitoneal lesions in four patients could have been misdiagnosed because the lesions were the same density as the distended small bowel, but differentiation was not difficult because of the capabilities of the workstation.

Another disadvantage of the lactulose solution is that it cannot be used in cases of trauma. This technique should not be used in suspected bowel trauma, and we did not use it to examine any patient with abdominal trauma.

We conclude that lactulose solution provides good distention of all the small-bowel loops from the jejunum to the ascending colon. Noninvasive peroral CT enterography performed with lactulose solution as an oral contrast material is a simple, rapid, and noninvasive method of evaluating small-bowel disease. This examination is a tubeless procedure, which improves patient comfort, that requires less time to perform, costs less, and decreases radiation exposure. It can also be used at routine abdominal examinations as a negative contrast agent instead of iodinated oral contrast medium, especially in CT angiography and cases of bowel bleeding and mesenteric thrombosis. Further research and clinical experience will define the precise role of CT enterography with lactulose in the investigation of inflammatory and noninflammatory small-bowel diseases in a larger group of patients.

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This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Arslan, H. Articles by Temizöz, O. Search for Related Content PubMed PubMed Citation Articles by Arslan, H. Articles by Temizöz, O. Social Bookmarking                      What's this?